308 - Bone Marrow Composition of Transgender Youth at Initiation of a Puberty Blocker: A Two Site Study

Carly Guss, Boston Children's Hospital, Boston, MA, United States; Amy D. DiVasta, Boston Children's Hospital, Mansfield, MA, United States; Mekibib Altaye, Cincinnati Children's Hospital Medical Center, CINCINNATI, OH, United States; Halley M. Wasserman, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; R Korkodilos, Boston Children's Hospital, Boston, MA, United States; Leah Tyzinski, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States; Sridhar Vajapeyam, Boston Children's Hospital, Boston, MA, United States; Kirsten Ecklund, Boston Children's Hospital, Boston, MA, United States; Robert v. Mulkern, Children's Hospital, Boston Harvard Medical School, Boston, MA, United States; Heidi Kalkwarf, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States

Background: Gonadotropin-releasing hormone agonists (GnRHa) are a mainstay of treatment for transgender youth. Disordered eating behaviors are more common in transgender youth than among cisgender peers. Bone marrow composition affects bone strength. Little is known about baseline bone marrow composition prior to initiation of GnRHa treatment.

Objective: To determine bone marrow composition of transgender youth at the initiation of a GnRHa and the relation to nutritional status compared to cisgender peers.

Design/Methods: Peri-pubertal transgender children consented to initiate GnRHa and cisgender controls matched by age and body mass index (BMI) were enrolled from Boston Children's Hospital and Cincinnati Children’s Hospital. Participants were eligible if Tanner II-III, did not have a chronic illness, and were not using medications that affected bone health. Transgender participants had a study visit within 6 weeks of initiation of a GnRHa. Eating disorder behaviors were assessed using the Eating Attitudes Test (EAT-26) survey. Bone mineral density (BMD) was assessed by dual energy X-ray absorptiometry (DXA), and bone marrow composition was measured by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) of the left knee. T1 ratio was assessed with MRI as a marker of marrow fat content. Statical analyses included t-tests, chi-square and Pearson correlations.

Results: Forty-one transgender youth and 37 cisgender controls were recruited. There were no differences in history of fractures (p=0.24) or history of osteoporosis (p=0.29) between groups. BMD Z-scores at the total body (-0.95 vs 0.11, p< 0.0001) and spine (0.03 vs 0.82, p=0.006) was lower in transgender youth compared to controls. The normalized T1 ratio, defined as T1 of bone divided by T1 of muscle, was also lower in transgender youth vs. controls (0.54 vs 0.58, p=0.024). Both groups had similar self-reported calcium and vitamin D intake. Transgender participants had a higher EAT-26 score (7.15 vs 3.65, p=0.003); however, the threshold for clinical referral (score >20) was not met for any participant. Pearson correlation analyses did not reveal any significant association between bone marrow assessments with age, BMI or EAT-26 score.

Conclusion(s): Prior to initiation of pubertal blockade, transgender youth had lower total body and spine BMD Z-scores compared to cisgender controls. They also had lower T1 scores consistent with higher marrow fat. Bone marrow findings may explain differences in BMD. Counseling regarding optimizing bone health is important for transgender youth.